J/ApJ/725/480 Stellar X-ray sources in the COSMOS survey (Wright+, 2010)
Stellar X-ray sources in the Chandra COSMOS survey.
Wright N.J., Drake J.J., Civano F.
<Astrophys. J., 725, 480-491 (2010)>
=2010ApJ...725..480W 2010ApJ...725..480W
ADC_Keywords: Stars, G-type ; Stars, late-type ; Photometry, infrared ;
Photometry, SDSS ; Spectral types ; X-ray sources ; Surveys
Keywords: binaries: close - Galaxy: halo - stars: activity - stars: coronae -
stars: late-type - X-rays: stars
Abstract:
We present an analysis of the X-ray properties of a sample of solar-
and late-type field stars identified in the Chandra Cosmic Evolution
Survey (COSMOS), a deep (160ks) and wide (∼0.9deg2) extragalactic
survey. The sample of 60 sources was identified using both
morphological and photometric star/galaxy separation methods. We
determine X-ray count rates, extract spectra and light curves, and
perform spectral fits to determine fluxes and plasma temperatures.
Complementary optical and near-IR photometry is also presented and
combined with spectroscopy for 48 of the sources to determine spectral
types and distances for the sample. We find distances ranging from
30pc to ∼12kpc, including a number of the most distant and highly
active stellar X-ray sources ever detected. Overall the sample is
typically more luminous than the active Sun, representing the
high-luminosity end of the disk and halo X-ray luminosity functions.
The halo population appears to include both low-activity spectrally
hard sources that may be emitting through thermal bremsstrahlung, as
well as a number of highly active sources in close binaries.
Description:
In this paper, we present a sample of stellar X-ray sources identified
in the Chandra survey of the COSMOS field (Elvis et al. 2009, Cat.
J/ApJS/184/158), including an analysis of their properties.
Optical and near-IR observations are from the COSMOS optical catalogs:
http://cosmos.astro.caltech.edu/data/
Spectra for objects in our sample were compiled from a number of
sources. An additional 35 spectra (for sources with r≤17) were
obtained using the FAST spectrograph, on the 1.5m Tillinghurst
telescope, equipped with a 300gpm grating, resulting in a resolution
of ∼3Å and a wavelength coverage of 3480-7400Å.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 126 60 X-ray properties of stellar sources detected in
the Chandra COSMOS survey
table2.dat 148 60 Optical and near-IR properties of stellar
sources detected in the Chandra COSMOS survey
--------------------------------------------------------------------------------
See also:
II/284 : COSMOS Multi-Wavelength Photometry Catalog (Capak+, 2007)
J/A+A/542/A16 : Radio star forming and AGN X-ray properties (Ranalli+, 2012)
J/ApJ/716/348 : The XMM-Newton survey of the COSMOS field (Brusa+, 2010)
J/ApJS/184/218 : The zCOSMOS 10k-bright spectroscopic sample (Lilly+, 2009)
J/ApJS/184/158 : Chandra COSMOS survey I. (Elvis+, 2009)
J/ApJ/696/1195 : COSMOS AGN spectroscopic survey. I. (Trump+, 2009)
J/ApJS/172/383 : AGN candidates in the COSMOS field (Trump+, 2007)
J/ApJS/172/70 : zCOSMOS-bright catalog (Lilly+, 2007)
http://cosmos.astro.caltech.edu/data : COSMOS online archive
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 h RAh Optical hour of right ascension (J2000) (1)
4- 5 I2 min RAm Minute of right ascension (J2000)
7- 11 F5.2 s RAs Second of right ascension (J2000) (1)
13 A1 --- DE- Optical sign of declination (J2000)
14 I1 deg DEd Optical degree of declination (J2000)
16- 17 I2 arcmin DEm Arcminute of declination (J2000)
19- 22 F4.1 arcsec DEs Arcsecond of declination (J2000)
24- 28 I5 --- CID Chandra COSMOS id (Seq number from
Cat. J/ApJS/184/158,
in Simbad)
30- 36 F7.2 ct Ncts Net counts in the full (0.5-8keV) band
38- 41 F4.1 ct E_Ncts Upper 1σ error on Ncts
43- 46 F4.1 ct e_Ncts Lower 1σ error on Ncts
48- 51 F4.1 --- Sig Source detection significance
53- 57 F5.2 [-] logP Log of the probability that the source is a
chance coincidence of background events (2)
59- 64 F6.2 ks Exp Full exposure time (3)
66- 69 F4.2 keV Emed Median energy in the full (0.5-8keV) band (4)
71- 76 F6.2 [-] logPKS Log of the Kolmogorov-Smirnov probability
that the source is not variable
78- 79 A2 --- Fit [1T/- ] X-ray spectral model fit type (5)
81- 85 F5.2 keV kT ? Thermal plasma temperature of model fit (6)
87- 90 F4.2 keV E_kT ? Positive error on kT (6)
92- 95 F4.2 keV e_kT ? Negative error on kT (6)
97-102 F6.2 [mW/m2] logF Log of the X-ray flux in the full band (7)
104-107 F4.2 [mW/m2] E_logF ? Upper 1σ error on logF
109-112 F4.2 [mW/m2] e_logF ? Lower 1σ error on logF
114-119 F6.2 [mW/m2] logFs ? Log of extinction-corrected soft
(0.5-2.0keV) X-ray flux
121-126 F6.2 [mW/m2] logFh ? Log of extinction-corrected hard
(2.0-8.0keV) X-ray flux
--------------------------------------------------------------------------------
Note (1): The RAs of this table have lot of errors (in column 7, some "0" have
replaced the good number). These coordinates should be ignored,
the correct ones are given in table 2.
Note (2): Logarithm of the Poisson probability that the source is a chance
coincidence of background events. Values below -6 are listed as -6.0.
Note (3): Full exposure time for each source derived from the mono-energetic
exposure maps for the combined observations.
Note (4): Background-corrected median energy of all source photons in the full
(0.5-8.0keV) band.
Note (5): X-ray spectral model fit type: single-temperature thermal plasma model
(1T) or no model fit (-).
Note (6): Thermal plasma temperature of model fit with upper and lower
90% confidence intervals (uncertainties missing when they are so large
that the parameter is effectively unconstrained).
Note (7): Logarithm of the extinction-corrected X-ray flux in the full
(0.5-8.0keV) band from model fit or derived from the number of net
counts for unfit sources as described in Section 2. Upper and lower
1σ errors are shown or left blank when the upper or lower bounds
are unconstrained. For sources without model fits, the flux errors are
not specified individually.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 h RAh Optical hour of right ascension (J2000)
4- 5 I2 min RAm Minute of right ascension (J2000)
7- 11 F5.2 s RAs Second of right ascension (J2000)
13 A1 --- DE- Optical sign of declination (J2000)
14 I1 deg DEd Optical degree of declination (J2000)
16- 17 I2 arcmin DEm Arcminute of declination (J2000)
19- 22 F4.1 arcsec DEs Arcsecond of declination (J2000)
24- 28 I5 --- CID Chandra COSMOS number identification
30- 36 F7.4 mag umag ? SDSS u-band magnitude
38- 43 F6.4 mag e_umag ? umag uncertainty
45- 50 F6.3 mag gmag ? SDSS g-band magnitude
52- 56 F5.3 mag e_gmag ? gmag uncertainty
58- 63 F6.3 mag rmag ? SDSS r-band magnitude
65- 69 F5.3 mag e_rmag ? rmag uncertainty
71- 76 F6.3 mag imag ? SDSS i-band magnitude
78- 82 F5.3 mag e_imag ? imag uncertainty
84- 89 F6.3 mag zmag ? SDSS z-band magnitude
91- 95 F5.3 mag e_zmag ? zmag uncertainty
97-102 F6.3 mag Jmag 2MASS J-band magnitude
104-108 F5.3 mag e_Jmag Jmag uncertainty
110-115 F6.3 mag Hmag ? 2MASS H-band magnitude
117-121 F5.3 mag e_Hmag ? Hmag uncertainty
123-128 F6.3 mag Ksmag 2MASS Ks-band magnitude
130-134 F5.3 mag e_Ksmag Ksmag uncertainty
136-138 A3 --- SpT MK spectral type
139 A1 --- q_SpT [*] *: low-quality spectra, accurate to
±2 subtypes
141-142 A2 --- r_SpT Origin of spectral classification (8)
144-148 F5.2 kpc Dist Estimated distance based on spectral type
--------------------------------------------------------------------------------
Note (8): Source of spectral classification as follows:
F = FAST spectrograph on the 1.5m Tillinghurst telescope at the Fred
Lawrence Whipple Observatory, Mount Hopkins, Arizona (resolution of
∼3Å and wavelength coverage of 3480-7400Å).
V = VIMOS (VIsible MultiObject Spectrograph/Very Large Telescopre; Lilly et
al. 2007, Cat. J/ApJS/172/70 and 2009, Cat. J/ApJS/184/218).
I = IMACS (Inamori Magellan Areal Camera and Spectrograph (IMACS)/Magellan;
Trump et al. 2007, Cat. J/ApJS/172/383 and 2009, Cat. J/ApJ/696/1195)
VI = VIMOS+IMACS
p = photometric
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Emmanuelle Perret [CDS] 07-Aug-2012